They are synthetic, and like any PH/DS/AAS there's a correlation with excessive use and left ventricle hypertrophy. Of course, lifting heavy weights is also correlated with left ventricle hypertrophy. Some actually think it's not the PH/DS/AAS that causes the heart hypertrophy, but rather that it allows you to lift heavier weights.

Either way, if you want to get huge, there are going to be certain risks. If you just want to be healthy/fit, there are better avenues than anabolics involving diet and exercise as well as some other OTC supplements like Na-R-ALA, ALCAR, probiotics, Krill oil, etc.